Fix display user not updating locally until app restart

Engines now read user.name from the config object at transcription time
instead of caching it at init, so name changes take effect immediately.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app_controller.py

@@ -276,7 +276,6 @@ class AppController:
         self.current_model_size = model
         self.current_device_config = device_config
 
-        user_name = self.config.get('user.name', 'User')
         continuous_mode = self.config.get('transcription.continuous_mode', False)
 
         if continuous_mode:
@@ -293,7 +292,6 @@ class AppController:
         if remote_mode in ('managed', 'byok'):
             self.transcription_engine = DeepgramTranscriptionEngine(
                 config=self.config,
-                user_name=user_name,
                 input_device_index=audio_device,
             )
             self.transcription_engine.set_callbacks(
@@ -343,7 +341,7 @@ class AppController:
                 initial_prompt=self.config.get('transcription.initial_prompt', ''),
                 no_log_file=self.config.get('transcription.no_log_file', True),
                 input_device_index=audio_device,
-                user_name=user_name,
+                app_config=self.config,
             )
             self.transcription_engine.set_callbacks(
                 realtime_callback=self._on_realtime_transcription,